Vacuum forming machine

ABSTRACT

A vacuum forming machine comprises a base structure, a porous plate spacedly mounted on the base structure, and a blower mounted on the base for drawing air through the porous plate. A clamping frame for plastic sheets conforms closely to the perimetric contour of the porous plate. The frame is pivoted for movement to a heating element on the base and to the porous plate, which is then inserted through an opening in the frame. A leveling arrangement is mounted on the frame and/or the porous plate, for spacing the frame from the base and for aligning the frame with the adjacent edge of the porous plate.

[45 Mar. 14, 1972 United States Patent Knack, Sr.

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Southfield, Mich.

July 9, 1970 Primary Examiner.l. Howard Flint, Jr. Attorney-Don J. Smith[22] Filed:

[21] Appl. No.:

[57] ABSTRACT A vacuum forming machine comprises a base structure, aporous plate spacedly mounted on the base structure, and a 18/19F blowermounted on the base for drawing air through the porous plate. A clampingframe for plastic sheets conforms 5 m M7 1 m 5 8 n 5 2 4 0% s 3 5 2 [52]U.S. [51] Int. [58] Field of References Cited closely to the perimetriccontour of the porous plate. The frame is pivoted for movement to aheating element on the UNITED STATES PATENTS base and to the porousplate, which is then inserted through an opening in the frame. Aleveling arrangement is mounted on the frame and/or the porous plate,for spacing the frame from the base and for aligning the frame with theadjacent edge of the porous plate.

7 Claims, 7 Drawing Figures FFF 999 111 III 888 1.11

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LBHR 678457 255666 999999 111111 l/l/l/ 736 45 Patented March 14, 1972 2Sheets-Sheet l e m w w Patented March 14, 1972 3,549,152

2 Sheets-Sheet 2 H Ha mon/144% DESCRIPTION OF THE INVENTION The presentinvention relates to vacuum forming machines for shaping thin,substantially twodimensional plastic sheets into three-dimensionalshapes or forms, and more particularly to amachine having an improvedsheet holder or frame for positioning the plastic sheet properly withrespect to the mold or other forming means of the machine.

Vacuum forming machines germane to the machine of the characterdescribed have been known for some time and generally include a hingedor pivoted frame in which a twodimensional, sheet of thermoplastic orformable plastic is clamped. The frame can be moved to a first positionrelative to a heating element of the machine wherein the plastic sheetis heated to its softening temperature The frame can then be moved to asecond or forming position in the machine, relative to a vacuum pan. Oneor more mold structures or forming members are disposed on the vacuumpan which is sufficiently porous that air can be drawn therethrough by ablower or the like forming part of the vacuum forming machine The moldstructures are provided with suitable aperture means communicating withthe porous surface structure of the vacuum pan. The heated plastic sheetis drawn and shaped about the mold structures by air passing through thevacuum pan to create a partial vacuum between the plastic sheet and thevacuum pan, and other vacuum components of the machine. Similarly thesheet is drawn into the various crevices or indentations in the moldstructure by the aforementioned aperture means.

In the operation of such vacuum machines, it is highly desirable toorient the plastic sheet holder or frame properly with respect to thevacuum pan such that the shaped portions of the plastic sheet areproperlyoriented with respect to the balance or unformed portions of thesheet. In a typical vacuum forming machine, it is highly desirable,therefore to maintain the plane of the plastic sheet holder or framesubstantially parallel to the vacuum pan. In previous machines, noadequate means has been provided for this purpose, with the inevitableresult that the residual tensil strength of the heated plastic sheet isutilized in many cases to support or partially support the frame orholder with respect to the vacuum pan, usually at a raised positionabove the top surface of the base structure of the machine.

The pivoted frame or holder likewise is maintained slightly above thetop surface of the machine to allow a proper pivotal movement thereof.As the plastic sheet and frame must be moved quickly from the heatingelement ofthe machine to the vacuum structure or vacuum pan thereof,little time is allowed for the operator of the machine to orientate oralign manually the frame relative to the vacuum pan. In the operation ofthe vacuum forming machines, then, one side or other of the plasticsheet holder or frame may be permitted to sag with respect to the vacuumpan with the result that the formed areas of the sheet are misorientatedrelative to the perimeter or other relatively unformed areas of theplastic sheet. The three-dimensional image imparted to the sheet,moreover, is frequently distorted.

Likewise, the operator of the machine in an attempt to prevent theoccurrence of the aforementioned frame sagging, may inadvertently andmanually support the frame or a side thereof at some position slightlyabove the vacuum pan. A loss or partial loss of the partial vacuum,which would otherwise be developed between the plastic sheet and thesuctional passages of the machine, then occurs and the plastic sheet maybe only partially formed about the mold structure or other formingmembers placed on the vacuum pan.

I overcome these disadvantages by providing self-aligning means on theplastic sheet holder or frame and/or on the vacuum pan structure of themachine. The self-aligning means does not interfere with the normaloperation of the vacuum forming machine, in particular its pivotal framestructure. Rather, the alignment means insures in a repetitive mannerthe levelling of the frame structure with the vacuum pan each time theframe structure is placed thereover, Most importantly, theself-alignment means does not interfere with the proper orientation ordisposition of both the frame structure and the vacuum pan at theirraised positions above the base structure of vacuum forming machine.

I accomplish these desirable results by providing in avacuum formingmachine, the combination comprising a base structure for said machine, aporous plate structure spacedly mounted on said base structure, duct andblower means mounted on said base structure for drawing air through saidplate structure, a clamping frame for plastic sheet material and thelike, said frame conforming closely to the perimetric contour of saidporous plate structure, means for mounting and pivotally moving saidframe from a first position on said base structure adjacent a heatingelement thereof to a second position whereat said plate structure isinserted through an opening in said frame, and means secured to at leastone of said frame and said plate structure for engaging and aligningsaid frame relative to said plate structure at said second positron.

I also desirably provide a similar vacuum forming machine wherein saidengaging and aligning means include at least three bracket memberssecured to said plate structure and spaced thereabout for engagement byand alignment of said frame member.

I also desirably provide a similar vacuum forming machine wherein saidbracket members are each secured to a bottom surface of said platemember and include an outward, downwardly stepped section positioned toengage said frame and to align upper edge portions of said frame with anupper perimeter of said plate structure.

I also desirably provide a similar vacuum forming machine wherein saidengaging and aligning means include a bracket member secured to saidplate structure and at least one foot member secured to said framemember and engageable with an adjacent surface of said base structure tospace said frame member therefrom.

During the foregoing discussion, various objects, features andadvantages of the invention have beenset forth. These and other objects,features and advantages of the invention together with structuraldetails thereof will be elaborated upon during the forthcomingdescription of certain presently preferred embodiments of the inventionand presently preferred methods of practicing the same.

In the accompanying drawings I have shown certain presently preferredembodiments of the invention and have illustrated certain presentlypreferred methods of practicing the same, wherein:

FIG. 1 is an isometric view of one form of vacuum forming machinearranged in accordance with the invention and showing the frame in anintermediate position FIG. 2 is a similar view with the frame in theheating position;

FIG. 3 is a similar view with the frame in the forming position;

FIG. 4 is a partial enlarged elevational view, partially sectioned, ofthe apparatus as shown in FIG. 2;

FIG. 5 is a similar view of the apparatus as shown in FIG. 3;

FIG. 6 is a front elevational view of a vacuum forming machine similarto that shown in FIG. 1, but illustrating another form of the invention;and

FIG. 7 is an enlarged partial isometric view of the apparatus as shownin FIG. 6.

With reference now to FIGS. 1-5 of the drawings, a vacuum formingmachine 10 shown therein comprises a base structure 12, which houses aheating element 14 in a heating well or recess 16. A screen 18 or thelike, covers the top opening of the well 16 to prevent inadvertentcontact with the heating element 14.

The base structure 12 also houses a blower (not shown) and suitablecontrols therefor, for drawing air through the vacuum pan or porousplate structure 20. The vacuum pan 20 is spaced above the vacuum formingmachine 10, as better shown in FIG. 2 by means of a low profile duct 22(FIGS. 2 and S) which adjoins the porous plate 20 adjacent itsperimeter. The duct 22 together with other air passages (not shown) inthe base structure 12 conducts air drawn through the vacuum pan 20 tothe aforementioned blower.

A plastic sheet holder or frame 24 is pivotally mounted on the basestructure 12 and is spaced above the surface thereof (FIG. 1) to permitalignment of the frame 24 with the vacuum pan 20. The frame hinges 26 inthis example are of the pantographic variety to facilitate suchalignment. The frame proper includes in this example a rectangular shapeof angle material 28 and a complementary rectangular member 30 of asuitable complementary cross section and seatable therein. Thecomplementary member 30 is hinged at 31 to the angle 28 for the purposeof clamping a plastic sheet 32 therebetween.

The plastic sheet holder 24 can be swung about the pivot means 26 to aposition (FIGS. 2 and 4) whereat the plastic sheet 32 is closelydisposed above the heating well 16. After the plastic sheet softens, theholder 24 is quickly moved to its position generally surrounding theperiphery of the vacuum pan 20 as shown (FIGS. 3 and The aforementionedblower is then actuated to withdraw air through the vacuum pan or porousplate structure 20 and duct 22 (arrows 34). The sof tened plastic sheet32 then is drawn downwardly, over, and around mold structure 36 or othershaping elements (not shown) to impart a corresponding three-dimensionalshape to the plastic sheet 32.

The forming of the plastic sheet 32 is facilitated by aperture means 38in the mold structure 36, which apply suction to specific areas betweenthe plastic sheet 32 and the adjacent surfaces of the mold structure 36.The aperture means 38 for example can be disposed at various recessesand indentations or the like defining the design or message imparted tothe mold structure 36.

When the frame 24 is positioned about the vacuum pan 20, it is highlydesirable that the frame be properly aligned or levelled with the vacuumpan 20. This assures that those perimetric portions 320 (FIG. 5) of thesheet 32 will flushly engage the perimetric edges 20a of the vacuum pan20. If the frame 24 and plastic sheet are not initially so aligned,either ridges or depressions will appear in the plastic sheet 32 at thevacuum pan edges 20a of varying elevations, depending on whether theadjacent portion of the frame is depressed below or raised upon therelated edge 20a of the vacuum pan. In ad dition to the unsightlycharacter of these ridges or depressions, the form or shape imparted tothe plastic sheet 32 by the mold structure 36 will be angularlymisorientated relative to the base or perimetric portions 32a of theplastic sheet. Moreover, if one or more sides of the frame 24 isinadvertently elevated above the vacuum pan 20 a substantial quantity ofair can enter the resulting spaces between the adjacent sheet edge 32aand the vacuum pan edge 20a, resulting in a partial or complete loss ofthe partial vacuum necessary for the forming operation. In consequence,the sheet 32 when formed may exhibit a partial vacuum necessary for theforming operation. In consequence, the sheet 32 when formed may exhibita partial or complete loss of definition.

One form of such levelling means includes, in this example, athree-point suspension for the frame 24 in the forming position thereof,as illustrated in FIGS. 1-3 and 5. Such suspension means assures properalignment of the frame 24 and the heated plastic sheet 32, which issupported by the frame, with the vacuum pan 20. In this arrangement,such suspension means include an angle bracket 40 secured to theunderside of the vacuum pan 20 at its edge adjacent the hinges 26. Asevident from FIG. 5, the angle bracket 40 is shaped such that theadjacent portions of the frame 24 seat flushly therein with the adjacentperimetric edge portion 32a of the plastic sheet being disposedsubstantially flush with the adjacent edge portions 20a of the vacuumpan 20.

The front corners portions 42 (FIG. I) of the frame 24 are provided withfeet 44, which can be in the form of grommets or the like (FIG. 5). Thefeet 44 are of such elevation that the adjacent portions of the frame 24are supported at the proper elevations by contact of the feet 44 withthe adjacent upper surfaces of the base structure 12 of the vacuumforming machine I0. Thus, the front corners 42 and the remainder of theframe structure 24 are likewise aligned with the vacuum pan 20 such thatthe perimetric edge portions 320 of the sheet 32 flushly engage theperimetric edges 200 about the entire perimeter of the vacuum pan 20.The alignment of the frame 24 in this manner is facilitated by thethree-point suspension thereof, including the angle bracket 40 and thefeet or grommets 44, relative to the vacuum pan 20. The hinge or pivotmembers 26 can be spring or gravity loaded (for example by conventionalpins and vertical slots) to allow the frame 24 to be thus positioned bythe three-point suspension means, particularly the adjacent anglebracket 40. With the arrangement as shown in FIGS. 1-5, it is virtuallyimpossible for the frame 24 or any part thereof to be inadvertentlypositioned above or below the vacuum pan 20 such that the aforementionedridges or recesses will appear in the sheet 32 at the vacuum pan edges200 or such that vacuum leakage will occur at one or more of theseedges.

It is contemplated that other arrangements of the aforementioned framesuspension means can be employed within the context of my invention. Forexample, the feet or grommets 44 of FIGS. 1-5 can be replaced by anglebrackets similar to the bracket 40 (FIG. 5). As shown in FIG. 6, theplastic sheet holder or frame 24' is supported adjacent its front comerportions 42' by a pair of angle brackets 46 respectively. Each of thebrackets 46 is secured in this example beneath the vacuum pan 20 forproper engagement by the frame 24. The brackets 46 can be secured (bysheet metal screws or the like) to a supporting flange 48 of the airduct 22'. The brackets 46, which are disposed adjacent the front comersof the vacuum pan 20 and remote from the hinges 26, together with theangle bracket 40 (FIG. 5) thus form a desirably three-point suspensionof the frame 24 in alignment with the vacuum pan 20' as describedpreviously. In this arrangement, the angle brackets 46 extend from thesides of the vacuum pan 20 adjacent the front corners thereof as bettershown in FIG. 7. The brackets 40, 46 in addition support the frame 24'at the proper spacing above the adjacent upper surface of the basestructure 12 of the vacuum forming machine 10.

Other modifications of the suspending means are contemplated within theteachings of my present invention. For example, the brackets 40, 46 ofFIG. 5 and 6 can each be replaced by a foot or grommet similar to thefoot 44 (FIGS. 1-5) at each corner of the frame 24. Likewise, the anglebracket 40 (FIG. 5) can be removed and its function replaced by a pairof angle brackets similar to the brackets 46 of FIGS. 5 and 6 disposedadjacent the rear corners of the vacuum pan 20'.

Relative to FIGS. 1-5, the angle bracket 40 can extend the entire lengthof the adjacent edge portion of the vacuum pan 20. It is preferred,however, that the angle bracket be considerably shorter for examplenominally about the width of the angle bracket 46 of FIGS. 5 and 6, anddisposed adjacent the midpoint of the adjacent edge of the vacuum pan20, in order to afford a desirably three-point suspension of the frameor holder 24. The three-point suspension of course, facilitates theself-alignment of the frame 24 when it is moved from its heatingposition (FIG. 2) to its forming position (FIG. 3).

From the foregoing it will be apparent that novel and efficient forms ofVacuum Forming Machine have been described herein. While I have shownand described certain presently preferred embodiments of the inventionand have illustrated presently preferred methods of practicing the same,it is to be distinctly understood that the invention is not limitedthereto but may be otherwise variously embodied and practiced within thespirit and scope of the invention.

I claim:

1. In a vacuum forming machine, the combination comprising a basestructure for said machine, a porous plate structure spacedly mounted onsaid base structure, duct and blower means mounted on said basestructure for drawing air through ncAn said plate porous structure, aclamping frame for plastic sheet material and the like, said frameconforming closely to the perimetric contour of said porous platestructure, means for mounting and pivotally moving said frame between afirst position on said base structure adjacent a heating element thereofand a second position whereat said plate structure is inserted throughan opening in said frame, and at least one foot member mounted on alower surface of said frame remote from said hinge means, said footmember being engageable with an adjacent surface of said base structurefor spacing said frame therefrom and for aligning said frame with theadjacent edge of said plate member.

2. The combination according to claim 1 wherein a pair of said footmembers are provided, said foot members being secured to said frameadjacent corner sections thereof remote from said hinge means.

3. The combination according to claim 2 wherein a frame supportingbracket is secured to said plate structure at a location remote fromsaid feet members for engagement and alignment of the adjacent portionof said frame.

4. In a vacuum forming machine, the combination compris ing a basestructure for said machine, a porous plate structure spacedly mounted onsaid base structure, duct and blower means mounted on said basestructure for drawing air through said plate porous structure, aclamping frame for plastic sheet material and the like, said frameconforming closely to the perimetric contour of said porous platestructure, means for mounting and pivotally moving said frame from afirst position on said base structure adjacent a heating element thereofto a second position whereat said plate structure is inserted through anopening in said frame, and means secured to at least one of said frameand said plate structure for engaging and aligning said frame relativeto said plate structure at said second position.

5. The combination according to claim 4 wherein said engaging andaligning means include at least three bracket members secured to saidplate structure and spaced thereabout for engagement by and alignment ofsaid frame member.

6. The combination according to claim 5 wherein said bracket members areeach secured to a bottom surface of said plate member and include anoutward, downwardly stepped section positioned to engage said frame andto align upper edge portions of said frame with an upper perimeter ofsaid plate structure.

7. The combination according to claim 4 wherein said engaging andaligning means include a bracket member secured to said plate structureand at least one foot member secured to said frame member and engageablewith an adjacent surface of said base structure to space said framemember therefrom.

1. In a vacuum forming machine, the combination comprising a basestructure for said machine, a porous plate structure spacedly mounted onsaid base structure, duct and blower means mounted on said basestructure for drawing air through said plate porous structure, aclamping frame for plastic sheet material and the like, said frameconforming closely to the perimetric contour of said porous platestructure, means for mounting and pivotally moving said frame between afirst position on said base structure adjacent a heating element thereofand a second position whereat said plate structure is inserted throughan opening in said frame, and at least one foot member mounted on alower surface of said frame remote from said hinge means, said footmember being engageable with an adjacent surface of said base structurefor spacing said frame therefrom and for aligning said frame with theadjacent edge of said plate member.
 2. The combination according toclaim 1 wherein a pair of said foot members are provided, said footmembers being secured to said frame adjacent corner sections thereofremote from said hinge means.
 3. The combination according to claim 2wherein a frame supporting bracket is secured to said plate structure ata location remote from said feet members for engagement and alignment ofthe adjacent portion of said frame.
 4. In a vacuum forming machine, thecombination comprising a base structure for said machine, a porous platestructure spacedly mounted on said base structure, duct and blower meansmounted on said base structure for drawing air through said plate porousstructure, a clamping frame for plastic sheet material and the like,said frame conforming closely to the perimetric contour of said porousplate structure, means for mounting and pivotally moving said frame froma first position on said base structure adjacent a heating elementthereof to a second position whereat said plate structure is insertedthrough an opening in said frame, and means secured to at least one ofsaid frame and said plate structure for engaging and aligning said framerelative to said plate structure at said second posItion.
 5. Thecombination according to claim 4 wherein said engaging and aligningmeans include at least three bracket members secured to said platestructure and spaced thereabout for engagement by and alignment of saidframe member.
 6. The combination according to claim 5 wherein saidbracket members are each secured to a bottom surface of said platemember and include an outward, downwardly stepped section positioned toengage said frame and to align upper edge portions of said frame with anupper perimeter of said plate structure.
 7. The combination according toclaim 4 wherein said engaging and aligning means include a bracketmember secured to said plate structure and at least one foot membersecured to said frame member and engageable with an adjacent surface ofsaid base structure to space said frame member therefrom.